1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus incorporating the same. More particularly, the invention relates to an ink jet recording head that discharges ink as a liquid and an ink jet recording apparatus incorporating the same.
2. Related Art
A known ink jet recording head, as an example of a liquid ejecting head, includes an actuator unit, a nozzle plate and a flow channel unit. The actuator unit includes piezoelectric elements and pressure generating chambers. The nozzle plate communicates with the pressure generating chambers and includes nozzle orifices for discharging ink. The flow channel unit includes a reservoir-forming substrate in which a reservoir is formed as a common ink chamber for the pressure generating chambers (see JP-A-2004-042559, pages 6 to 8 and FIGS. 1 and 2, for example).
In such an ink jet recording head, pressure applied to the ink in a pressure generating chamber generates a pressure wave within a pressure generating chamber. The pressure wave propagates to the reservoir which is in communication with the pressure generating chambers. The pressure wave propagates to other pressure chambers via the reservoir, which may cause variation in ink jet characteristics including a droplet ejection rate.
To address this problem, an ink jet recording head has been proposed in which the pressure wave is attenuated within the reservoir so as to prevent further propagation to other pressure generating chambers. With this configuration, variation in ink jet characteristics including a droplet ejection rate is controlled (see JP-A-2007-145014, pages 10 to 12 and FIG. 4, for example). In particular, energy of the pressure wave is absorbed by a compliance section formed as a thinned portion at an area corresponding to the reservoir. The compliance section has a pressure fluctuation absorbing function (hereinafter, referred to as “compliance”).
The reservoir includes an inflow port for introducing ink at a central area along a direction in which the pressure generating chambers are arranged in parallel. When seen in plan view, the width of the reservoir is constant in the central area and is reduced at both end areas along a direction perpendicular to the direction in which the pressure generating chambers are arranged in parallel.
In a reservoir having a constant width across the full length thereof, a flow rate of the ink introduced in the central area decreases while moving toward both end areas of the reservoir. This may cause air bubbles to become entrapped in both end areas. To address the entrapment, the reservoir has the above-described configuration.
There is also a problem of deficient compliance in the narrowed areas of the reservoir. The compliance section fails to provide a desired vibration control effect.
Although an ink jet recording head has been illustrated, such a problem also exists in liquid ejecting heads for ejecting liquids other than ink.